This invention relates to an equipment using a micro-actuator applicable in medical instruments and optical instruments.
In order to provide an equipment which can be inserted in a small space where conventional equipments are not accessible and to provide an equipment which can control a very fine movement with a required precision, miniaturization of machine parts has become necessary.
Fine processing engineering using technics of fabricating silicon integrated circuits, has supplied technics for fabricating micro electro mechanical systems. Thus, a micro rotor of about 100 .mu.m diameter is rotated or an object of a similar dimension is linearly displaced. The present invention relates to such micro-actuators and manufacturing process thereof.
Prior arts of the above-mentioned micro-actuators are disclosed on "Laterally Driven Resonant Microstructures" in 1989 of HEMS (Micro Electro Mechanical Systems) (pp53.about.59), on "IC-Processed Electrostatic Micro-motors" by Long-Sheng Fan et al in 1988 IEEE (pp666.about.669), on "Single Crystal Silicon Micro-Actuators" by K. Suzuki in 1990 IEEE (pp625.about.628), and in a Japanese Patent Application (laid-open Publication No. Hei3-230780) filed by the same applicant of this invention on Feb. 2, 1990, and published on Oct. 12, 1991.
In these conventional devices, a stator unit is fixed on a substrate, and a movable unit is floatingly supported by the substrate. An electro-static force exerting between the stator unit and the movable unit, drives the movable unit. Since the mass of the movable unit is very small, the movable unit has a very high resonant frequency with a sharp resonance character.
But, in all rotary types of micro-actuators of the prior arts, it is not easy to transmit the rotation of the movable part to an external object. This is because of the fact that the movable unit (or the rotor unit) is surrounded by the stator unit in a same plane.
Linear displacement type of movable unit can be easily connected to an external device since there is no obstruction in the direction of the linear motion. But, rotary motions are primarily required to the microactuators, the difficulty of transmitting the rotary motion to an external object, is a restriction of prior art devices.